Accurate and reliable monitoring of radioactivity levels is an important part of working with or near to radioactive materials, and in particular, but not exclusively, in the nuclear industry. Moreover, there is an increasing demand for improved safety and increased product performance, including having monitoring apparatuses that may be required to be certified. For example, monitoring apparatus may be required to have a so-called Safety Integrity Level (SIL) in accordance with IEC61508. Thus, it would be desirable to provide an improved radioactivity monitoring apparatus fulfilling all these and any associated needs.